TF indicates high voltage frequency converter, M indicates the motor of condensate pump; The relationship of electric blocking and logic blocking exists between 4 QF  and 1QF,  between 5 QF and QF,  between  4QF and 5 QF( when 4QF is opened, 5QF is allowed to close; when 5QF is opened,4QF is allowed to close) in order to prevent short circuit at output side of high-voltage frequency converter and 6kV power supply side. 1QF, 2QF and 3QF are the existing facilities in the site, 3QF, 4QF and 5QF only have manually switching-on function. The high-voltage switch 3QF of high-voltage  frequency converter is installed in ""of high voltage switch 3 QF installed on "Auxiliary  6 kV transformer room", and it is connected with the busbar. Two DC control power sources and two power DC sources of all the switches in "High- voltage frequency converter" are supplied by # 2 unit DC busbar. 

When 1 # pump is in variable frequency operation, disconnect  1QF, close 3QF and 4QF switch, and the 1 # condensate pump is in variable frequency operation state; 2 # condensate pump in standby state of power frequency. When the variable frequency operation of 1 # condensate pump  breaks down and trips, the system will interlock start 2 # condensate pump , and 2 QF switch will operate at industrial frequency. When 2 # pump is in variable frequency operation, disconnect 2  QF, close 3QF and 5QF switches, and 2 # condensate pump is in state of variable frequency operation; 1 # condensate pump in standby state of power frequency. When the variable frequency operation of 2 # condensate pump breaks down and trips, the system will interlock start 1 # condensate pump , and 1 QF switch will operate at industrial frequency.